Polymerization of conjugated diolefinic hydrocarbons to drying polymers



Patented PeuZ, 11941 I I v v I I p POLYMERIZATION CONJUGATED DIOLE- 1IJIIE IIgJIYDROCARBOlilS T DRYING POLY- Henry s. Rothrock, Wilmington, per, assignor tms. 1.;

E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application October 4, 1939, Serial No. 297,955

9 Claims. (Cl. 260-93) v This invention relates to the polymerization processes. Other objects of the'invention will of aliphatic open-cha conjugated diolefinic appear hereinafter.

hydrocarbons, such as utadiene and its homo- I These objects are accomplished by subjecting logs to form soluble, viscous, oily polymers posan aliphatic open-chain conjugated, diolefin, sessing drying properties, and has particular particularly butadiene, in solvent quantities of reference to efiecting the polymerization to dryan inert hydrocarbon to a temperature between ing polymer in the presence of a metallic sodium 100 to 170- C. under pressure in the presence or similar catalyst. Moreparticularly, the .inof appreciable quantities of a sodium or other vention comprises a process for effecting relacatalyst from the group consisting of the alkali tively rapid polymerization of butadiene and its 10 metal and alkaline earth metals. In the prehomologs to drying polymers under certain seferred embodiment of this invention a 20% to lected and correlated conditions of temperature, 40% solution of a hydrocarbon of the butadiene proportion of catalyst and dilution with an inseries, asbutadiene, in a non-reactive hydroert hydrocarbon solvent. carbon, as benzene, or a mixture of the satu- Previous efiorts have been made to obtain synrated and unsaturated four carbon hydrocarbons thetic products possessing the drying characin petroleum cracking processes, is subjected for teristics of the various naturally occurring sica few hours to a temperature between 110 to cative oils, such as linseed, soya bean, oiticica, 150 C., under pressure, in the presence of sodium China wood and the like. In such prior atinv an amount approximating at least 4% to tempts it has been proposed to polymerize butaabout 14% by weight of said butadiene hydrodiene and its homologs by the use of metallic carbon.

sodium and alkali metal catalysts. In some of f It is essential that appreciable quantities of these processes only caoutchouc-like materials the sodium or other catalyst be used in contrast are formed. In other methods using alkali to amounts of .3 to 1% of catalyst employed in metals as catalysts, it has been found necessary prior methods wherein rubbery types of polymers to immediately remove the polymerized products are produced. The catalyst is desirably present as soon as they are formed, the yields are exin quantity approximating at least 4% to about tremely low, and the products are inferior, and 14% by weight of butadiene or other aliphatic at times contaminated with rubbery polymer. open-chain conjugated diolefin employed in the Furthermore, these prior methods with sodium polymerization reaction. Although metallic soor other alkali metal catalysts require a numdium, because of its low cost and ready availaber of days to carry out the polymerization rebility, is the preferred catalyst for use in this action, invention, other alkali 'metal or alkaline earth This invention has as an object the provision metals may be used, such as lithium, potassium,

of a method for obtaining drying polymers by calcium'and the like. These metals may be used the polymerization of aliphatic open-chain consingly or as mixtures or alloys with one another. jugated diolefinic hydrocarbons particularly Or instead of the free metals, their hydrides butadiene and its homologs, in the presence of may be used, such as sodium hydride which is sodium or other alkali metal, or alkaline earth particularly desirable for this use because of its metal catalyst. [Another object is to providev a ready availabilityin a fine state of division.

method for transforming such aliphatic open- It is important that solvent quantities of a chain conjugated diolefinic hydrocarbons into nonreactive hydrocarbon be used, that is, the drying polymers having excellent characteristics diolefin should be diluted with at least equal with respect to rate of drying and nature of parts or approximately 50% or more of a hydrofilms formed. A further object is to provide a carbon which is substantially free from particimethod of obtaining such drying polymers in pation in the reaction. The diolefin or butaexcellent yield and substantially free from the diene concentration of the solutions employed in relatively useless or undesirable by-products the polymerization may preferably contain 20% frequently obtained by other methods. A 'still to 40% diolefin or butadiene. As solvents, there further object is to effect a relatively rapid may be employed benzene, one or more satupolymerization-of butadiene and its homologs to rated or mono-olefinic aliphatic hydrocarbons,

improved drying polymers. Another important for example, a mixture of four carbon saturated object is to provide a method for polymerizing and unsaturated aliphatic hydrocarbons obbutadiene-butylene mixtures, which mixtures tained in petroleum cracking processes, or are readily obtainable from petroleum cracking hydro-aromatic hydrocarbons, such as cycloand mesitylene.

- 3 hours at 110 C.

hexane and cyclohexene. It is not desirable to use as solvents aromatic hydrocarbons having one or more aliphatic side chains attached to the aromatic nucleus, such as toluene,- xylene Such aromatic hydrocarbons having side chains condense with diolefins in the presence of alkali metals to form large quantities of alkylene substituted benzenes.

As the polymerizing temperature is one of the somewhat critical conditions essential to the process or this invention, it should be approximately between 100 to 170 C., and preferably between 110 to 150 C. to secure most successful wresults jllire selected-IeactiQnQtempe ture ha a marked effect upon character of product and yields oi drying polymer. Temperatures below 100 C. produce negligible quantities of drying polymers 'whereas temperatures above 170 C. produce a dark, gelled mass and substantially none of the desired drying polymer.

The method 01' this invention comprises the use of dilute solutions of butadiene, appreciable percentages of sodium or similar catalyst, preferably in amount at least 4% to about 14% by weight ofbutadiene, and a reaction temperature of at least 100 C. but not more than 170 C. The polymerization of butadiene to drying polymer in excellent yields is rapidly obtained by a proper correlation of temperature, amount of catalyst and dilution of butadiene with inert hydrocarbon solvent in accordance with the method oi this invention.

The process oi thisinvention is applicable to polymerize aliphatic open-chain condugated diolefinic hydrocarbons, particularly a hydrocarbon of the butadiene series. For example, the diolefinic constituent may be butadiene or various open-chain homologs of butadiene, such as isoprene, a-methyl butadiene (piperylene), or 2,3-dimethyl butadiene. These butadiene hydrocarbons may be employed alone or in mixture with butadiene or with each other.

Such homologs oi butadiene, which are equivalents-ior butadiene in the present invention, are therefore comprehended within the meaning of the term a conjugated butadiene as used here- Also there may be used in this invention butadiene-olefin and butadiene-containing aliphatic hydrocarbon mixtures, such as can be separated from the low boiling constituents produced in the cracking of petroleum hydrocarbons.- By fractionation of these low boiling constituents there are obtained fractions containing butsparts ethyl alcohol and 4 parts activated charcoal, after which this mixture is heated for 80 minutes at steam bath temperature, and again filtered through filtercel.

Volatile material is then evaporated from the filtrate on a water bath, leaving 33 parts oi a deep red, viscous, oily polymer. This polymer, which has an iodine number of approximately 400, is readily soluble in organic hydrocarbgn/ solvents: such asi lLiu oleum ethen'muene, xylene, benzene m neral spirits and the like.

bination of these drying accelerators and elevated temperatures.

Example 11 when 150 parts 01' a butylene-butadiene mixture containing 32% butadiene and 5 parts sodium metal are subjected to the treatmentdescribed in Example I except that the heating is carried out for 4 hours at 140 0., there is obtained a 75% yield (based on butadiene) of polymer similar in properties with that of the first example. The term butylene as used herein refers to a mixture oi four carbon hydrocarbons, for example, l-butene, 2-butene, n-butane, 2- methyl propane, 2-methyl propene-l, which are obtained in addition to butadiene in petroleum cracking processes.

from such mixtures is a tedious and expensive process, it is desirable to use the mixtures without furth'er treatment.

The invention is illustrated by the following examples in which parts are by weight-unless otherwise specified.

Example I A pressure bomb is loaded with 35 parts butadiene, 105 parts benzene, and 5 parts metallic sodium, placed in a shaker rack and heatedior The bomb is then cooled, and the reaction product filtered through a kieselguhr filter-aid, such as filterceP' to remove sodium. To the filtrate is then added 7.5

Example III when a mixture of 25 parts benzene, 125 parts butylene-butadiene solution containing 32% butadiene, and 5 parts sodium is treated as described in Example II,there is obtained an yield (based on butadiene) oi polymer similar in properties to that of Example I. As illustrative of the critical eiiect 0! temperature on this reaction, a mixture 01' 35 parts of benzene, 125 parts of butylene-butadiene solution containing 32% of butadiene, and 5 parts oi. sodium heated for 5 hours at C. in a closed vessel as in Example 1, yields only 5% of drying polymer. A similar reaction carried out at 90' C. gives only a negligible yield of drying polymer.

Example 1V When 25 parts of butadiene, 150 parts benzene, and 1 part sodium are heated for 1% hours at C. and treated as described in Example I, there is obtained a 76% yield (based on butadiene) of drying polymer.

Example V when 40 parts butadiene, 80 parts benzene, and 5 parts or sodium hydride are heated for 3 hours at (2., and treated as described in Example I there is obtained a 77.5% yield (based on butadiene) of drying polymer similar in characteristics to that obtained by the procedure of Example I.

It is preferable to carry out the polymerization under the pressure exerted by the reaction components at the temperature employed. However, higher pressures may be employed and these higher pressures may be obtained by having preswater or of other solvents.

the conditions employed for the polymerization,

and in many cases it is possible thus to effect some modification in the properties of the butadiene drying polymers. Among the materials which may be employed in small proportion for this purpose are indene, dihydronaphthalene, chloroprene, styrene, vinyl acetate, methyl methacrylate, and other unsaturated compounds. Cyclic diolefins, such as cyclopentadiene and 1 cyclohexadiene may also be employed in smal proportions with butadiene.

To recover the drying polymer the crude reaction product may be filtered, preferably through some absorbent agent such as flltercel." Before filtration, it may be desirable to add more solvent to the crude reaction product. From the filtrate there is evaporated (under vacuum if desired) the volatile material to yield the non-volatile, viscous polymer as a residue. that the boiling point of the hydrocarbon or hydrocarbons employed as solvent be sufiiciently low to permit ready removal during the purification of the product.

Alternatively the filtrate may be treated with a small amount of alcohol or with water or with .dilute acid solutions, heated for a few minutes.

with activated charcoal, and then refiltered prior to the evaporation of the volatilematerial from the filtrate. This alternative treatment gener- It is preferable ally results in a somewhat lighter colored and more rapid drying product. The color of the product is also improved if air'is carefully excluded until after the treatment with alcohol, water, or acid.

The synthetic drying polymers prepared from butadiene or other aliphatic open-chain conjugated diolefinic hydrocarbons in accordance with the method of this invention may be utilized for the various decorative and protective purposes for which drying oils or vehicles of a drying nature are commonly employed. A solution of the drying polymer may be employed directly as a clear varnish or lacquer. For example, steel panels may be brushed or sprayed in the customary manner with a solution of the polymer in an appropriate hydrocarbon solvent, such as xylene or mineral spirits.

Such films show good drying characteristics and dry rapidly at ordinary or elevated temperatures, and even more rapidly if there is present a small amount (16 to {is per cent based on the weight of polymer present) of the customary drying accelerators, such as the naphth'enates or linoleates of ,cobalt, lead or manganese. The coatings obtained are smooth, glossy, clear, colorless, hard and adherent. They show no indications of cracking or loss of adhesion when the metal support is bent, and are remarkably resistant to the action of acids, alkalis, and of Outdoor exposures have shown that the coatings possess good durability characteristics. Solutions of the drying polymer .in suitable solvents may be applied to other surfaces, such as wood or over various base coats. Such coatings possess excellent gloss, adhesion and durability.

Solutions of the drying polymer are particularly suitable for uses which involve baking at relatively high temperatures around 200 C p for instance. Drying is very rapid under these conditions, particularly in thin films, and there are formed hard, chemically resistant coatings which possess considerable flexibility. Thus, the solutions of the drying polymer are especially suitable for coating the interior of food cans, beverage containers and the like.

For such purposes the polymers may serve particularly well when employed as undercoats in conjunction with other top-coating materials. When a vinyl chloride-vinyl acetate interpolymer is employed as a top coat, it may be desirable to incorporate with the solution of butadiene polymer a small proportion, e.' g., 1% to 10% of a methacrylic acid ester, such as isobutyl methacrylatefin order to promote-superior adhesion to the top coat.

Solutions of the drying polymer may also be used as vehicles for the preparation of enamels. For example, 100 parts of a 60% solution of the drying polymer from butadiene in mineral spirits is ground with '75 parts of titanium dioxide to produce an enamel of excellent whiteness and hiding power. This enamel coatin may be air dried or baked, yielding a smooth, glossy, coating of desirable appearance and durability. A black enamel having similar desirable properties is prepared by grinding together 100 parts of the drying oil polymer solution and 7 parts of carbon 1 black.

The rapid accomplishment of the polymerization to drying polymer by the method of this invention is one of its important advantages. This rapidity with which the polymerization is effected constitutes a decided improvement over prior methods. With this invention it is possible to effect practically complete polymerization of butadiene to a drying polymer in a few hours time, whereas prior methods require 3 days or more. Furthermore this invention does not require careful control of the course of the polymerization in order to stop the reaction prior to occurrence ofsolid products as in prior methods. Another important advantage of this invention is the formation of high yields of drying polymer by polymerizing'butylene which is readily available at low cost from the petroleum industry.

The use of appreciable amounts of catalyst in this invention is one of the important features 'for securing soluble drying polymers from diolefins and involves no unduev expense since most of the catalyst may readily be recovered for reuse from the soluble reaction products at the remove the finely divided sodium from the rubbery reaction products formed in such prior methods. Another advantage of this invention is the high yields of improved drying polymers and substantial absence of solid or rubbery polymer in the reaction product.

As many apparently widely different embodiments this invention may be made without departing from the spirit and scope thereof, it is to be understood that-I do not limit myself to the specific embodiments thereof, except as de fined in the appended claims.

I claim:

1. A process for rapidly polymerizing a conjugated butadiene to drying polymers which comprises subjecting a concentration of 20 to 50% of said conjugated butadiene in an inert hydrocarbon solvent to a temperature of 110 to 170 C. under pressure in the presence of a catalyst selected from the group consisting of the alkali metals, the alkali metal hydrides and the alkaline earth metals, said catalyst being present in an amount approximating at least 4% to about 14% by weight of said conjugated butadiene.

2. The process set forth in claim 1 in which said catalyst is metallic sodium.

3. The process set forth in claim 1 in which said catalyst is sodium hydride.

4. A process for rapidly polymerizing a conjugated butadiene to drying polymers which comprises subjecting a concentration of 20 to 50% of said conjugated butadiene in butylene to a temperature of 110 to 170 C. under pressure in the presence of a catalyst selected from the group consisting of the alkali-metals, the alkali metal hydrides and the alkaline earth metals, said catalyst being present in an amount approximating at least 4% to about 14% by weight of said conjugated butadiene.

5. The process set forth in claim 4 in which said catalyst is metallic sodium.

6. The process set forth in claim 4 in which said catalyst is sodium hydride.

7. A process for rapidly polymerizing a conjugated butadiene to drying polymers which comprises subjecting a mixture of aliphatic hydrocarbons derived from the cracking of petroleum and containing 20 to 50%'of a conjugated butadiene in said aliphatic hydrocarbons to a tailperature of to C. under pressure in the presence or a catalyst selected from the group consisting of the alkali metals, the alkali metal hydrides and the alkaline earth metals, said catalyst being present in an amount approximating at least-4% to about 14% by weight of said conjugated butadiene.

8. A process for rapidly polymerizing a con- Jugated butadiene to drying polymers which comprises subjecting a butadiene-olefin mixture sep-- arated from the low boiling constituents produced in the cracking of petroleum hydrocarbons and containing 20 to 50% of a conjugated butadiene in said olefin mixture to a temperature of 110 to 170 C. under pressure in the presence 01 a catalyst selected from the group consisting of the alkali metals, the alkali metal hydrides and the alkaline earth metals, said catalyst being present in an amount approximating at least 4% to about 14% by weight of said conjugated butadiene.

9. A process for rapidly polymerizing a conjugated butadiene to drying polymers which comprises subjecting a concentration of 20 to 50% of said conjugated butadiene in a mixture of saturated and unsaturated tour carbon hydrocarbons derived from the cracking of petroleum hydrocarbons to a temperature of 110? to 170C. under pressure in the presence of a catalyst selected from the group consisting of the alkali metals, the alkali metal hydrides and the alkaline earth metals, said catalyst being present in an amount approximating at least 4% to about 14% by weight of said conjugated butadiene.

HENRY S. RO'I'IEOCK. 

